Showing papers on "Anodic bonding published in 2006"

Adhesive wafer bonding

Abstract: Wafer bonding with intermediate polymer adhesives is an important fabrication technique for advanced microelectronic and microelectromechanical systems, such as three-dimensional integrated circuits, advanced packaging, and microfluidics. In adhesive wafer bonding, the polymer adhesive bears the forces involved to hold the surfaces together. The main advantages of adhesive wafer bonding include the insensitivity to surface topography, the low bonding temperatures, the compatibility with standard integrated circuit wafer processing, and the ability to join different types of wafers. Compared to alternative wafer bonding techniques, adhesive wafer bonding is simple, robust, and low cost. This article reviews the state-of-the-art polymer adhesive wafer bonding technologies, materials, and applications.

Method of fabrication of ai/ge bonding in a wafer packaging environment and a product produced therefrom

Abstract: A method of bonding of germanium to aluminum between two substrates to create a robust electrical and mechanical contact is disclosed. An aluminum-germanium bond has the following unique combination of attributes: (1) it can form a hermetic seal; (2) it can be used to create an electrically conductive path between two substrates; (3) it can be patterned so that this conduction path is localized; (4) the bond can be made with the aluminum that is available as standard foundry CMOS process. This has the significant advantage of allowing for wafer-level bonding or packaging without the addition of any additional process layers to the CMOS wafer.

III-nitride light emitting devices fabricated by substrate removal

Abstract: Devices and techniques for fabricating InAlGaN light-emitting devices are described that result from the removal of light-emitting layers from the sapphire growth substrate. In several embodiments, techniques for fabricating a vertical InAlGaN light-emitting diode structure that result in improved performance and or cost-effectiveness are described. Furthermore, metal bonding, substrate liftoff, and a novel RIE device separation technique are employed to efficiently produce vertical GaN LEDs on a substrate chosen for its thermal conductivity and ease of fabrication.

Prolog to Wafer Direct Bonding: From Advance Substrate Engineering to Future Applications in Micro/Nanoelectronics

Abstract: Wafer direct bonding refers to the process of adhesion of two flat mirror-polished wafers without using any intermediate gluing layers in ambient air or vacuum at room temperature. The adhesion of the two wafers occurs due to attractive long range van der Waals or hydrogen bonding forces. At room temperature the bonding energy of the interface is low and higher temperature annealing of the bonded wafer pairs has to be carried out to enhance the bonding energy. In this paper, we describe the prerequisites for the wafer-bonding process to occur and the methods to prepare the suitable surfaces for wafer bonding. The characterization techniques to assess the quality of the bonded interfaces and to measure the bonding energy are presented. Next, the applications of wafer direct bonding in the fabrication of novel engineered substrates such as "silicon-on-insulator" and other "on-insulator" substrates are detailed. These novel substrates, often called hybrid substrates, are fabricated using wafer bonding and layer splitting via a high dose hydrogen/helium implantation and subsequent annealing. The specifics of this process, also known as the smart-cut process, are introduced. Finally, the role of wafer bonding in future nanotechnology applications such as nanotransistor fabrication, three-dimensional integration for high-performance micro/nanoelectronics, nanotemplates based on twist bonding, and nano-electro-mechanical systems is discussed

Adhesive Bonding of InP ∕ InGaAsP Dies to Processed Silicon-On-Insulator Wafers using DVS-bis-Benzocyclobutene

Abstract: The process of bonding InP/InGaAsP dies to a processed silicon-on-insulator wafer using sub-300 nm layers of DVS-bis-benzocyclobutene (BCB) was developed. The planarization properties of these DVS-bis-BCB layers were measured and an optimal prebonding die preparation and polymer precure are presented. Bonding quality and bonding strength are assessed, showing high-quality bonding with sufficient bonding strength to survive postbonding processing.

Study of PMMA thermal bonding

Abstract: The bond strength dependence on bonding temperature and bonding pressure in traditional thermal bonding and surface modification bonding of PMMA is investigated. The results show that the bond strength of the latter bonding method is larger than the former. The effects of post-annealing and aging on bond strength are also demonstrated. Then the bonding parameters of temperature and pressure are optimized, and typical bond strength of 1 MPa is obtained at bonding temperature of 95°C, bonding pressure at 2 MPa, bonding time for 3 min and 50°C post-annealing for 2 h. The successful bonded microfluidic device was obtained through this optimized thermal bonding method.

Microfluidic channel fabrication by PDMS-interface bonding

Abstract: A novel technique for bonding polymer substrates using PDMS-interface bonding is presented in this paper. This novel bonding technique holds promise for achieving precise, well-controlled, low temperature bonding of microfluidic channels. A thin (10–25 µm) poly(dimethylsiloxane) (PDMS) intermediate layer was used to bond two poly(methyl methacrylate) (PMMA) substrates without distorting them. Microchannel patterns were compressed on a PMMA substrate by a hot embossing technique first. Then, PDMS was spin-coated onto another PMMA bare substrate and cured in two stages. In the first stage, it was pre-cured at room temperature for 20 h to increase the viscosity. Subsequently, it was bonded to the hot embossed PMMA substrate. In the second stage, PDMS was completely cured at 90 °C for 3 h and the bonding was successfully achieved at this relatively low temperature. Tensile bonding tests showed that the bonding strength was about 0.015 MPa. Microfluidic channels with dimensions of 300 µm × 1.6 cm × 100 µm were successfully fabricated using this novel bonding method.

The development of Cu bonding wire with oxidation-resistant metal coating

Abstract: Although Cu bonding wire excels over Au bonding wire in some respects such as production costs, it has not been widely used because of its poor bondability at second bonds due to surface oxidation. We conceived an idea of electroplating oxidation-resistant metal on the Cu bonding wire to prevent the surface oxidation. The electroplating of Au, Ag, Pd, and Ni over Cu bonding wire all increased bond strengths as expected, but it caused problematic ball shapes except Pd-plated Cu bonding wire. The wire could produce the same ball shape as that of Au bonding wire. It was also proved to have excellent bondability sufficient to replace Au bonding wire. That is, it excelled in bond strengths, defective bonding ratio, and wideness of "Parameter Windows". It also showed the same stability as Au bonding wire in reliability tests, while bonds of Cu bonding wire were deteriorated in a few of the tests. In short, the Pd-plated Cu bonding wire can realize excellent bonding similar to Au bonding wire, while having much lower production costs.

Black silicon—new functionalities in microsystems

Abstract: Black silicon and its application as a new assembly method for silicon wafers at room temperature is presented. Needle-like structures on the surface after deep reactive ion etching with a length of 15–25 µm and 300–500 nm in diameter interlock with each other to form a bonding interface. After compression of two wafers at room temperature they generate retention forces up to 380 N cm−2 (3.8 MPa). If low contact forces are applied with partially interlocking of the needles, it is possible to generate a reversible Velcro®-like assembly. This new bonding process can be used for applications in the area of microfluidics with catalysts, microoptical or mechanical mountings or carrier wafer bonding in microelectronics.

Wafer level encapsulation of microsystems using glass frit bonding

Abstract: This paper gives an introduction to glass frit wafer bonding, which is an universally useable technology for encapsulation of microsystems, especially surface micromechanical sensors on wafer level. After a process description, some mechanical as well as electrical characteristics of glass frit bonded wafers are discussed and applications are shown.

Adhesive wafer bonding using partially cured benzocyclobutene for three-dimensional integration

Abstract: Wafer-level three-dimensional integration (3D) is an emerging technology to increase the performance and functionality of integrated circuits (ICs), with adhesive wafer bonding a key step in one of the attractive technology platforms. In such an application, the dielectric adhesive layer needs to be very uniform, and precise wafer-to-wafer alignment accuracy (similar to 1 mu m) of the bonded wafers is required. In this paper we present a new adhesive wafer bonding process that involves partially curing (cross-linking) of the benzocyclobutene (BCB) coatings prior to bonding. The partially cured BCB layer essentially does not reflow during bonding, minimizing the impact of inhomogeneities in BCB reflow under compression and/or any shear forces at the bonding interface. The resultant nonuniformity of the BCB layer thickness after wafer bonding is less than 1% of the average layer thickness, and the wafers shift relative to each other during the wafer bonding process less than 1 mu m (average) for 200 mm diameter wafers. When bonding two silicon wafers using partially cured BCB, the critical adhesion energy is sufficiently high (>= 14 J/m(2)) for subsequent IC processing.

Room temperature wafer level glass/glass bonding

Abstract: The findings of this study report the bonding of glass/glass wafers by using the surface activated bonding (SAB) method at room temperature (RT) without heating. In order to bond, the glass wafers were activated by a sequential plasma activation process, in which the wafers were cleaned with reactive ion etching (RIE) oxygen radio frequency (rf) plasma and nitrogen radical microwave (MW) plasma one after another and then contacted under hand-applied pressure followed by cold rolling under 20 kg load in atmospheric air. High bonding strength for glass/glass was achieved. Paramount influence of N 2 radical MW plasma on the adhesion enhancement of silicon/silicon bonding motivated the investigation of the N 2 radical MW plasma relationship with the bonding strength of glass/glass. A considerable influence of N 2 pressure on the bonding strength was not observed except in N 2 gas pressure of 30 Pa, which might be due to the debonding between glue and fixture used for tensile pulling test. No significant effect of OH density of glass wafers on the bonding strength was found below 400 °C. The result was evident from 400 °C and it was about twofold higher at 600 °C than that of RT to 400 °C. This result indicated that the sequential process bonding mechanism was consisting of long bridges of hydrogen bonding by water molecules. Significant environmental influence on the bonding strength was found and which could be correlated with OH molecules of glass wafers.

CNT Sensors for Detecting Gases with Low Adsorption Energy by Ionization.

Abstract: In case of typical chemical gas sensors reacted by gas adsorption on surface of an active layer, it is difficult to detect some gases which have low chemical adsorption energy like inert gases. In this paper, we report a gas sensor using carbon nanotube(CNT) array as electron emitters for the purpose of detecting these gases. Specifically, sensors were fabricated with applications of glass patterning by a sand-blast process and of anodic bonding between glass and silicon to improve the compactness of the structure and the reliability in process. The proposed sensor, based on an electrical discharge theory known as Paschen's law, worked by figuring the changes of dark discharge current and initial breakdown voltage depending on the concentration and the identity of gases. In this work, air and Ar gases were examined and discussed.

Room temperature SiO2∕SiO2 covalent bonding

Abstract: Room temperature covalent bonds between bonded silicon oxide layers can be realized by forming surface and subsurface absorption layers followed by terminating outmost bonding surfaces with desired bonding groups prior to bonding For example, by introducing fluorine into bonding oxide layers and NH2 groups onto surfaces of bonding oxide layers before bonding, bonding energy equivalent to silicon fracture energy (2500mJ∕m2) has been realized at room temperature after storage in air Fluorine incorporation causes Si–O–Si ring breaking leading to fluorinated oxide formation with lower density, thus facilitating a higher diffusion rate of polymerization by-products and enhanced moisture absorptivity Results indicate that by-products of the polymerization reaction between NH2 groups on mating surfaces appear to be more easily diffused and dispersed away from the bonding interface by the low density fluorinated oxide than are polymerization by-products of OH groups This enhanced by-product removal results in

Room-temperature microfluidics packaging using sequential plasma activation process

Abstract: A sequential plasma activation process consisting of oxygen reactive ion etching (RIE) plasma and nitrogen radical plasma was applied for microfluidics packaging at room temperature. Si/glass and glass/glass wafers were activated by the oxygen RIE plasma followed by nitrogen microwave radicals. Then, the activated wafers were brought into contact in atmospheric pressure air with hand-applied pressure where they remained for 24 h. The wafers were bonded throughout the entire area and the bonding strength of the interface was as strong as the parents bulk wafers without any post-annealing process or wet chemical cleaning steps. Bonding strength considerably increased with the nitrogen radical treatment after oxygen RIE activation prior to bonding. Chemical reliability tests showed that the bonded interfaces of Si/Si could significantly withstand exposure to various microfluidics chemicals. Si/glass and glass/glass cavities formed by the sequential plasma activation process indicated hermetic sealing behavior. SiOx Ny was observed in the sequentially plasma-treated glass wafer, and it is attributed to binding of nitrogen with Si and oxygen and the implantation of N2 radical in the wafer. High bonding strength observed is attributed to a diffusion of absorbing water onto the wafer surfaces and a reaction between silicon oxynitride layers on the mating wafers. T-shape microfluidic channels were fabricated on glass wafers by bulk micromachining and the sequential plasma-activated bonding process at room temperature

Deep reactive ion etching of borosilicate glass using an anodically bonded silicon wafer as an etching mask

Abstract: A new dry-etching method for fabricating anisotropic deep grooves on a borosilicate glass wafer is reported. The method uses a 200 µm thick bulk silicon wafer bonded to a borosilicate glass wafer by anodic bonding as an etching mask and inductively coupled plasma generated by C4F8 or CHF3 gases for etching. The measured etching rate showed that the deep reactive ion etching conditions for achieving a high etching rate are low gas pressure, high gas-flow rate, high antenna power and high bias power. The measured groove profile revealed that the sidewall angles of the etched grooves were less than 80° and C4F8 plasma provided a slight difference in width between the mask opening and etched groove. These results indicate that C4F8 plasma is suitable for precise groove fabrication. Even after fabrication of a 430 µm deep groove, enough silicon mask (135 µm thickness) remained to fabricate a deeper groove. Consequently, our etching method using an anodically bonded silicon mask and C4F8 plasma enables the fabrication of very deep grooves in borosilicate glass.

Bonding parameters of blanket copper wafer bonding

Abstract: A reliable copper wafer bonding process condition, which provides strong bonding at low bonding temperature with a short bonding duration and does not affect the device structure, is desirable for future three-dimensional (3-D) integration applications. In this review paper, the effects of different process parameters on the quality of blanket copper wafer bonding are reviewed and summarized. An overall view of copper wafer bonding for different bonding parameters, including pressure, temperature, duration, clean techniques, and anneal option, can be established. To achieve excellent copper wafer bonding results, 400°C bonding for 30 min. followed by 30 min. nitrogen anneal or 350°C bonding for 30 min. followed by 60 min. anneal bonding is necessary. In addition, by meeting the process requirements of future integrated circuit (IC) processes, the best bonding condition for 3-D integration can be determined.

Room temperature bonding of silicon and lithium niobate

Abstract: The feasibility of wafer-level bonding was examined for silicon (Si)/lithium niobate (LiNbO3) wafers by using a modified surface activated bonding process at room temperature. A low energy argon ion source of 80eV energy with 3A current was used, which was capable of sputter cleaning and depositing Fe nanolayers on the surfaces. Visual inspection showed that almost all of the 4in. Si∕LiNbO3 wafers were bonded. The measured bond strengths were as high as 37MPa but were inhomogeneous. This is due to the lack of uniform application of force over the surfaces (which are not parallel to the jigs) and the pulling angles during the pulling test. A 5nm thick amorphous layer was observed across the Si∕LiNbO3 interface. Electron energy loss spectroscopy analysis confirmed the presence of Fe in the interfacial amorphous layer. This Fe-containing interfacial layer appears to be responsible for the high bonding strength observed between Si∕LiNbO3 at room temperature.

Influence of Bonding Condition on Bonding Process Using Ag Metallo-Organic Nanoparticles for High Temperature Lead-Free Packaging

Abstract: We have proposed a novel bonding process using Ag metallo-organic nanoparticles with the average particle size of 11 nm, which can be the alternative to the current die-attach process using lead-rich high temperature solders. The metallurgical bonding between Ag and Cu can be achieved in Cu-to-Cu joints using the Ag metallo-organic nanoparticles at temperatures lower than 573 K. Bonding parameters of the Cu-to-Cu joints bondability were examined based on the measurement of the shear strength ofthe joints and the observation of the fracture surfaces and the cross-sectional microstructures. The joints using the Ag metallo-organic nanoparticles had the joint strength from 10 to 50MPa depending on bonding conditions. From the results, the bonding conditions providing the joint strength equivalent to those using the lead-rich high melting point solders were proposed.

Sealant, manufacturing process of glass panel and dye-sensitized solar cell

Abstract: PROBLEM TO BE SOLVED: To avoid the occurrence of damages such as cracks and breakage to glass substrates even made of soda lime glass, etc., in the manufacture of glass panels in which pasty sealant comprising glass powder is coated on the glass substrates to form sealing layers, two pieces of the glass substrates are bonded by irradiating the sealing layers with laser beam. SOLUTION: The sealant contains a laser absorbing component comprising not less than one kind of simple element or compound of any of chromium, iron, cobalt, manganese, copper and carbon and a glass component. The difference in coefficient of thermal expansion between the sealant and a material member to be sealed is ≤10×10 -7 /°C. Sealing layer 3 composed of the sealant is formed on sealing positions at least on one of the glass substrates 1. Another glass substrate 2 is laid on top of the substrate. The two glass substrates are bonded by melting the sealing layer by irradiating the sealing layer 3 with laser beam. COPYRIGHT: (C)2008,JPO&INPIT

Process and equipment for bonding by molecular adhesion

Abstract: The invention relates in a first aspect to a process for bonding by molecular adhesion of two substrates to one another during which the surfaces of said substrates are placed in close contact and bonding occurs by propagation of a bonding front between said substrates, characterised in that it comprises prior to bonding a step consisting of modifying the surface state of one and/or the other of said substrates so as to regulate the propagation speed of the bonding front. The surface state is modified by locally or uniformly heating the surface of one and/or the other of the substrates to be bonded, or again by roughing the surface of one and/or the other of the substrates.

Adhesive bonding with SU-8 at wafer level for microfluidic devices

Abstract: The present work proposes an adhesive bonding technique, at wafer level, using SU-8 negative photoresist as intermediate layer. The adhesive was selective imprint on one of the bonding surface. The main applications are in microfluidic area where a low temperature bonding is required. The method consists of three major steps. First the adhesive layer is deposited on one of the bonding surface by contact imprinting from a dummy wafer where the SU-8 photoresist was initially spun, or from a Teflon cylinder. Second, the wafers to be bonded are placed in contact and aligned. In the last step, the bonding process is performed at temperatures between 100 O C and 200 O C, a pressure of 1000 N in vacuum on a classical wafer bonding system. The results indicate a low stress value induced by the bonding technique. In the same time the process presents a high yield: 95-100%. The technique was successfully tested in the fabrication process of a dielectrophoretic device.

Bonding of glass-based microfluidic chips at low- or room-temperature in routine laboratory

Abstract: A low- or room-temperature bonding method was developed for fabrication of glass-based microfluidic chips without the requirement of clean environment and programmed high-temperature furnaces. After fundamental pretreatments, the glass substrates and cover plates to be bonded were sequentially soaked in concentrated sulfuric acid, washed with high-flow-rate tap water, de-ionized water and treated using HF steam as a necessary step. Finally, the plates were bonded by bringing the cleaned surfaces into close contact either under a continuous flow of de-ionized water or directly when treated with HF steam, and annealing at low-temperature ( 90%). The bonding quality of the chips was evaluated by employing SEM, shear strength testing procedure and electric current measurement at different applied voltages. The mechanism for the strong bonding strength was presumably related to the formation of a hydrolyzed layer on the glass plate surfaces after soaking them in acid or water for extended periods. Microfluidic chips bonded by the above method were evaluated in the CE separation of monofuctional reactive dye Cy5-labeled bioamines.

Comparison of medium-vacuum and plasma-activated low-temperature wafer bonding

Abstract: Two low-temperature wafer bonding methods, namely the medium-vacuum level wafer bonding (MVWB) and plasma-activated wafer bonding (PAWB), are performed. After low-temperature annealing (500°C) for a short time (<5h), the bond strength of these two low-temperature methods is improved as compared to the conventional air wafer bonding. The bond efficiency of MVWB is found to be better than the conventional air wafer bonding, but PAWB contains more bubbles. The qualitative mechanisms of these two low-temperature wafer bonding methods are proposed.

A glass microfluidic chip adhesive bonding method at room temperature

Abstract: This paper presents a novel method using UV epoxy resin for the bonding of glass blanks and patterned plates at room temperature. There is no need to use a high-temperature thermal fusion process and therefore avoid damaging temperature-sensitive metals in a microchip. The proposed technique has the further advantage that the sealed glass blanks and patterned plates can be separated by the application of adequate heat. In this way, the microchip can be opened, the fouling microchannels may be easily cleaned-up and the plates then re-bonded to recycle the microchip. The proposed sealing method is used to bond a microfluidic device, and the bonding strength is then investigated in a series of chemical resistance tests conducted in various chemicals. Leakage of solution was evaluated in a microfluidic chip using pressure testing to 1.792 × 102 kPa (26 psi), and the microchannel had no observable leak. Electrical leakage between channels was tested by comparing the resistances of two bonding methods, and the result shows no significant electrical leakage. The performance of the device obtained from the proposed bonding method is compared with that of the thermal fusion bonding technique for an identical microfluidic device. It is found that identical results are obtained under the same operating conditions. The proposed method provides a simple, quick and inexpensive method for sealing glass microfluidic chips.

Wafer bonding of damascene-patterned metal/adhesive redistribution layers

Abstract: Wafer bonding of patterned metal/adhesive layers, and related components, processes, systems and methods are disclosed.

Fabrication and validation of a multi-channel type microfluidic chip for electrokinetic streaming potential devices.

Abstract: To elaborate on the applicability of the electrokinetic micro power generation, we designed and fabricated the silicon-glass as well as the PDMS-glass microfluidic chips with the unique features of a multi-channel. Besides miniaturizing the device, the key advantage of our microfluidic chip utilization lies in the reduction in water flow rate. Both a distributor and a collector taking the tapered duct geometry are positioned aiming the uniform distribution of water flow into all individual channels of the chip, in which several hundreds of single microchannels are assembled in parallel. A proper methodology is developed accompanying the deep reactive ion etching as well as the anodic bonding, and optimum process conditions necessary for hard and soft micromachining are presented. It has been shown experimentally and theoretically that the silicon-based microchannel leads to increasing streaming potential and higher external current compared to those of the PDMS-based one. A proper comparison between experimental results and theoretical computations allows justification of the validity of our novel devices. It is useful to recognize that a material inducing a higher magnitude of zeta potential has an advantage for obtaining higher power density under the same external resistance.

Fluxless wafer bonding with Sn-rich Sn-Au dual-layer structure

Abstract: We report our initial result of bonding two 2 in. silicon wafers using Sn-rich Sn–Au dual-layer structure that is produced by electroplating process. No flux is used in the bonding process. Comparing to Au-rich Au80Sn20 eutectic alloy, it is more difficult to achieve fluxless feature using Sn-rich Sn–Au alloys due to tin oxidation. In this initial effort, two samples are produced. The resulting Sn-rich solder joint layer, about 30 μm in thickness, is very uniform over the entire 2-in. sample. The quality of the joint is examined using scanning acoustic microscope (C-SAM) and X-ray micro-imaging technique. Images of these two techniques indicate that the joints are of high quality. Of the two samples, the better one shows nearly perfect joint with only 2% of possible void area. This initial success shows that it is indeed possible to bond entire wafers together with a thin metallic joint of high quality. This fluxless technique can be extended to bonding wafers of different materials for new device and packaging applications. The use of metallic alloy layers of high melting temperature is also possible and is being considered.